New types of energy sources are needed to power electronic devices, electric vehicles and to smooth peak power demands on electric utilities. Promising devices for electrochemical energy conversion are based on the use of a solid electrolyte separator such as ceramic, beta alumina solid electrolyte (BASE).
Two high power density, high energy density, high efficiency electrochemical power systems based on a liquid sodium anode and beta or beta"-alumina solid electrolyte (BASE) have been intensely studied. The alkali metal thermoelectric converter operates at a hot side temperature of 1000-1300K. and is potentially the most efficient non-mechanical thermal to electric converter for this temperature range. The sodium-sulfur battery is an extremely high energy density secondary (rechargeable) battery operating at 600-700K.